The Attentional Capture Debate: When Can We Avoid Salient Distractors and When Not?

Abstract

There has been a long-standing debate concerning whether we are able to resist attention capture by salient distractors. The so-called "signal suppression hypothesis" of Gaspelin and Luck (2018) claimed to have resolved this debate. According to this view, salient stimuli "naturally attempt to capture attention", yet attention capture may be prevented by a top-down inhibitory mechanism. The current paper describes the conditions in which attention capture by salient distractors can be avoided. Capture by salient items can be avoided when the target is non-salient and therefore difficult to find. Because fine discrimination is needed, a small attentional window is adapted resulting in serial (or partly serial) search. Salient signals outside the focused attentional window do not capture attention anymore not because they are suppressed but because they are ignored. We argue that in studies that have provided evidence for signal suppression, search was likely serial or at least partly serial. When the target is salient, search will be conducted in parallel, and in those cases the salient singleton cannot be ignored nor suppressed but instead will capture attention. We argue that the "signal suppression" account (Gaspelin & Luck, 2018) that seeks to explain resistance to attentional capture has many parallels to classic visual search models such as the "feature integration theory" (Treisman & Gelade, 1980), "feature inhibition" account (Treisman & Sato, 1990), and "guided search" (Wolfe et al, 1989); all models that explain how the serial deployment of attention is guided by the output of earlier parallel processes.

Keywords: Attention; Learning; Visual search.

Figure 1

Illustration of search for a shape singleton target (diamond) when the target is salient (top of figure) and when the target is non-salient (bottom of Figure). When the target is salient, the attentional window is wide encompassing all items in the display. Because the target is salient it can be found by preattentive parallel search. During preattentive parallel search there is no top-down control and therefore the most salient singleton (the color singleton) captures attention. When the target is non-salient (bottom of Figure), the attentional window is reduced to be able to find the non-salient target. Because search proceeds serially in clumps, the color singleton no longer captures attention. Dependent on the difficulty of search, the size of clumps that are searched can vary while search proceeds (e.g., homogenous clumps of items can be discarded in large groups). Because the salient singleton no longer captures attention, selection is considered to be under top-down control.

Figure 2

Paradigm and data from Jonides and Yantis (1988). In the first display a target letter was displayed for 1000 ms (in this case the letter P) followed by a premask display for 1000 ms. In the search display one letter had a unique color (in this case red). At chance level this letter could be the target. The results show that observers did not start searching at the red letter even though it was highly salient (search functions for target uniquely colored and target not unique are identical).

Figure 3

Search displays of Stilwell & Gaspelin (2021). As in Jonides and Yantis (1988), the red singleton was ignored (mean search times for distractor present trials was 926 ms and distractor absent trials was 936 ms).

Figure 4

Paradigm and data from Theeuwes (2004). Observers search for a specific target feature (so-called feature search mode). At the top left: search for a diamond in displays consisting of either 5 or 9 nontarget elements; at the top right: search for a diamond in displays consisting of either 12 or 20 nontarget elements. At the bottom left: in small displays this leads to serial search and no interference of the color distractor; at the bottom right: it leads to parallel search (flat search functions) and a large inference of the color distractor (attentional capture of about 80 ms).